Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.74	6.142%	$83.5762	$83.58	$83.60	$83.60
Purchase #2	$20.33	4.639%	$21.2731	$21.27	$21.25	$21.30
Purchase #3	$39.78	7.797%	$42.8816	$42.88	$42.90	$42.90
Purchase #4	$18.75	8.739%	$20.3886	$20.39	$20.40	$20.40
Purchase #5	$114.48	8.279%	$123.9578	$123.96	$123.95	$124.00
Purchase #6	$168.67	8.409%	$182.8535	$182.85	$182.85	$182.90
Purchase #7	$217.46	6.543%	$231.6884	$231.69	$231.70	$231.70
7 purchase totals =	$658.21		$706.6192	$706.62	$706.65	$706.80